Magnetic encoder with two tracks

Magnetic encoder apparatus (1) for measuring the position of a readhead (9) relative to a magnetic scale (2)

• characterized in that
• the magnetic scale (2) comprises at least two magnetic tracks, namely the first magnetic track (3) with alternating magnetized regions (4) of the first type and magnetized regions (5) of the second type, wherein the magnetized regions (4) of the first type being the opposite magnetic pole to the magnetized regions (5) of the second type, thereby constituting number N1 of magnetic periods on the first magnetic track (3) along its length L1, and an additional magnetic track (6) with alternating magnetized regions (7, 7′) of the third type and magnetized regions (8, 8′) of the fourth type, wherein the magnetized regions (7, 7′) of the third type being the opposite magnetic pole to the magnetized regions (8, 8′) of the fourth type, thereby constituting number N2 of magnetic periods on the additional magnetic track (6) along its length L2;
• wherein the readhead (9) comprises a plurality of first magnetic sensor elements (11) for reading the magnetic signal of the first magnetic track (3), producing a plurality of first sensor signals, and a plurality of additional magnetic sensor elements (12) for reading the magnetic signal of the additional magnetic track (6), producing a plurality of additional sensor signals;
• wherein the first magnetic sensor elements (11) are designed in such a way so that at least one output periodic signal with N1′ signal periods is generated from the plurality of first sensor signals while the first magnetic sensor elements (11) move above periodically magnetized regions (4, 5) of the first magnetic track (11) along the length L1 of the first magnetic track (3);
• wherein the number N2 of the magnetic periods on the additional magnetic track (6) is increased or decreased by one period, or less than one period, relative to the number N1′ of signal periods generated by the plurality of the first magnetic sensor elements (11);
• and
• wherein one of at least two possible predefined data values is magnetically encoded into each magnetic period of the additional magnetic track (6), wherein the additional magnetic sensor elements (12) are designed for detecting the magnetically encoded data value.